Apparatus for electrochemically processing semiconductor substrates

ABSTRACT

A method of processing a semiconductor wafer is provided. The method includes introducing the wafer to a main chamber via a loading port, using a transfer mechanism to transfer the wafer to a first wafer processing module in a stack so that the wafer is disposed substantially horizontally in the first wafer processing module with a front face facing upwards, and performing a processing step on the front face of the wafer in the first wafer processing module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.15/876,300, filed on Jan. 22, 2018, which claims priority to UK PatentApplication No. 1701166.9, filed on Jan. 24, 2017, the entiredisclosures of which are incorporated by reference herein.

BACKGROUND

This invention relates to an apparatus for electrochemically processingsemiconductor substrates and to associated methods of electrochemicalprocessing. This invention has particular, but by no means exclusive,relevance to a plating apparatus, and to associated methods ofelectrochemical and electroless deposition onto semiconductorsubstrates.

Electrochemical or electroless deposition processes are frequently usedto form conducting layers in semiconductor device fabrication. Theseelectroplating techniques are useful in achieving void free filling ofvias, such as through silicon vias (TSVs), in particular for high aspectratio features. For example, copper interconnects may be formed byelectrochemical deposition during damascene processing. Similarly, Cu,Ni, SnAg and Au (among other metals) are known to be deposited ontosilicon or compound semiconductor substrates in semiconductor packagingapplications using electrochemical or electroless deposition methods.These plating techniques are applicable when semiconductors andcomponents are embedded in an epoxy mould such as in Fan out Wafer levelpackaging (FO-WLP). The emergence of embedded die formats such as FO-WLPenables the use of rectangular panel substrates to reduce manufacturingcosts.

Electrochemical deposition (ECD) processes in the semiconductor industrytypically include immersing an individual semiconductor wafer into anelectrolyte. A potential is applied between the wafer (acting as acathode) and a second electrode (acting as an anode) such that speciesin the electrolyte are deposited on the front face of the wafer.Typically the back face of the wafer is not exposed to the electrolyte.For the inverse process, that is electrochemical etching, the depositedlayer may be removed when the wafer is acting as an anode and the secondelectrode acts as a cathode.

In automated ECD systems, a robot arm typically collects thesemiconductor wafer from a loading/unloading port. This may be acassette or front opening unified pod (FOUP). The robot arm moves thewafer to a wafer holding fixture which creates an electrical contactwith the wafer. A fluid seal is formed between the wafer holding fixtureand the front face of the wafer to prevent any electrolyte fromcontaminating the electrical contacts or the back face of the wafer.

Two generic approaches are used to immerse the wafer in theelectrolyte—“fountain cell” and “rack” systems. In “fountain cell”systems the wafer is kept in a substantially horizontal plane duringprocessing. The wafer enters the electrolyte from above the depositionbath with the front face of the wafer (ie. the processing/depositionsurface) facing downwards. The electrolyte may be flowed in aperpendicular direction towards the front face of the wafer. The wafermay be rotated to establish a uniform diffusion layer thickness acrossthe wafer surface which helps to deposit a uniform layer. U.S. Pat. Nos.8,500,968 and 6,800,187 disclose “fountain cell” systems.

In “rack” systems the wafer is maintained in a substantially verticalplane and held statically in the electrolyte during processing.

For either the “fountain cell” or “rack” systems the electrolyte may becirculated within the electrolyte bath by means of a pump at relativelyhigh flow rates, for example at 8-40 litres per minute.

Multiple processing baths may be incorporated into a single waferprocessing system so that numerous processing steps may be performedsequentially to maximise wafer throughput. Processing steps couldcomprise multiple electrodeposition steps, such as deposition of acopper pillar with a Ni/SnAg cap; chemical etching steps; and numerousspin-rinse-drying (SRD), wetting and cleaning steps.

It is preferable for each processing bath to be easily accessible by theuser to permit maintenance and cleaning of the processing baths.Maintenance may comprise replacing the anode in an electroplating cell.Multiple processing baths for “fountain cell” and “rack” systems aretypically arranged in one or more rows such that each processing bathcan be accessed from high above by a robot arm on a linear track and bya user for maintenance. The wafer transport systems used in “fountaincell” and “rack” type systems may be complicated, often implementingwafer holding fixtures, an EFEM (equipment front end module) robot, andan overhead robot for transferring the wafer between processing bathsand clean stations. It would be desirable for the wafer transfer betweenprocessing baths to be simplified.

Advanced wafer processing systems often require a large number ofprocessing baths, potentially more than 20. A linear arrangement ofprocessing baths can result in the wafer processing system having alarge tool footprint, potentially more than 6 m in length.

SUMMARY

It is desirable to reduce the tool footprint of wafer processing systemsin wafer fabrication or semiconductor packaging facilities such that alarge number of processing steps may be performed with a high throughputand a minimal tool footprint.

It is also desirable to reduce the tool footprint of wafer processingsystems including multiple processing baths while maintaining easyaccess to each processing bath for maintenance and cleaning purposes.

It will be appreciated that, in addition to the specific problemsdescribed above, there is a general desire and need to reduce the toolfootprint of wafer processing systems. The present invention, in atleast some of its embodiments, addresses at least some of theseproblems, desires and needs.

According to a first aspect of the invention there is an apparatus forprocessing a front face of a semiconductor wafer comprising:

a main chamber;

at least one loading port connected to the main chamber for introducingthe wafer to the main chamber;

at least one stack of wafer processing modules comprising three or moresubstantially vertically stacked wafer processing modules, whereinadjacent wafer processing modules in the stack have a verticalseparation of less than 50 cm, and each processing module is configuredto process the wafer when disposed substantially horizontally thereinwith the front face of the wafer facing upwards, and at least one waferprocessing module is an electrochemical wafer processing module; and atransfer mechanism for transferring the wafer between the loading portand the processing modules.

Processing may comprise chemical and/or electrochemical processing.Processing may comprise one or more of etching, electrochemicaldeposition, electrochemical polishing, electroless deposition, rinsingsteps, cleaning steps, and drying steps. Thus, one of the processingmodules used in the apparatus may be an etching, electrochemicaldeposition, electrochemical polishing, electroless deposition, rinsing,cleaning, or drying module. One of the processing modules used in theapparatus may be a spin rinse dry module.

The semiconductor wafer may be a 300 mm silicon wafer, any othersuitable semiconductor substrate or a rectangular panel. The apparatusmay be suitable for processing a plurality of semiconductor wafers inparallel. The loading port may be a cassette or a FOUP (front openingunified pod).

The electrochemical wafer processing module may comprise a seal which,in use, seals against a surface to define a sealed cavity in whichelectrochemical processing takes place. The seal may be an elastomericseal.

In some embodiments, the seal, in use, seals against a surface of thewafer to define the sealed cavity in which electrochemical processingtakes place. Preferably, the surface of the wafer that the seal sealsagainst is an upper surface of the wafer.

The apparatus may further comprise at least one wafer carrierarrangement onto which the wafer can be loaded. The wafer carrierarrangement may comprise a seal which, in use, seals against a surfaceof the wafer. Preferably, this seal seals against an upper surface ofthe wafer. The transfer mechanism may be configured to transfer a loadedwafer carrier arrangement between the loading port and the processingmodules. In these embodiments, the seal of the electrochemical waferprocessing module may, in use, seal against a surface of the wafercarrier arrangement to define the sealed cavity in which electrochemicalprocessing takes place.

Typically, the wafer carrier arrangement also comprises an electricalcontact for making an electrical contact with a loaded wafer.

The apparatus may further comprise a wafer carrier arrangement loadingstation for loading the wafer onto the wafer carrier arrangement.Typically, the wafer carrier arrangement loading station also unloadsthe wafer once processing has been completed. The loading port maycomprise the wafer carrier arrangement loading station. Alternatively,the wafer carrier arrangement loading station may be positioned betweenthe loading port and the processing modules. Alternatively still, thewafer carrier arrangement loading station may be positioned prior to theloading port so that, when the wafer is introduced to the main chamber,the wafer is loaded onto the wafer carrier arrangement before passingthrough the loading port.

Adjacent processing modules in the stack preferably have a verticalseparation of less than 25 cm. The apparatus may comprise at least oneprocessing module that is not part of a stack.

The transfer mechanism may comprise a transfer robot having at least oneend effector for automated transfer of the wafer between the loadingport and the processing modules. The transfer mechanism may transfer thewafer between the loading port and any of the processing modules.

At least one of the wafer processing modules may comprise anelectrochemical deposition wafer processing module. The front face ofthe wafer may comprise an electrode. The electrochemical processingmodule may further comprise a second electrode. An electrical bias maybe applied to the wafer. The front face of the wafer may comprise acathode.

The processing modules may further comprise a tray positioned below theseal for collecting fluid.

The processing modules may be removable from the stack. The processingmodules may be independently removable from the stack. The removablenature of the processing modules may allow the processing modules to bereadily accessed for the purposes of maintenance, servicing and repairwork.

The processing modules may be removable from the stack in asubstantially horizontal direction. The processing modules may beremovable from the stack by rotating, sliding or by any other suitablemeans.

The apparatus may further comprise a blower for maintaining a laminarair flow in the main chamber.

The apparatus may further comprise a wafer alignment tool.

The apparatus may comprise at least three stacks. The at least threestacks may be arranged in rows or in any other suitable arrangement.

The apparatus may be configured to process the front face of two or moresemiconductor wafers in parallel.

According to a second aspect of the invention there is a method ofprocessing a semiconductor wafer using the apparatus according to claim1 comprising the steps of:

introducing the wafer to the main chamber via the loading port;

using the transfer mechanism to transfer the wafer to a first waferprocessing module in the stack so that the wafer is disposedsubstantially horizontally in the first wafer processing module with thefront face facing upwards; and performing a processing step on the frontface of the wafer in the first wafer processing module.

The method may comprise the further steps of: using the transfermechanism to transfer the wafer from the first wafer processing moduleto a second wafer processing module in the stack so that the wafer isdisposed substantially horizontally in the second wafer processingmodule; and performing a processing step on the front face of the waferin the second wafer processing module.

The method may comprise the further step of using the transfer mechanismto transfer the wafer from a wafer processing module to the loading portfor subsequent transfer out of the apparatus.

At least one processing step performed on the front face of the wafermay be selected from the group comprising a chemical, electrochemical,rinsing, cleaning, spinning, or drying step. The electrochemicalprocessing step may comprise optionally electrochemical deposition orelectrochemical etching. The electrochemical processing step isperformed in the electrochemical wafer processing module. Theelectrochemical wafer processing module may comprise a seal which sealsagainst a surface to define a sealed cavity in which electrochemicalprocessing takes place. The seal may seal against a surface of thewafer, preferably an upper surface of the wafer, to define the sealedcavity in which electrochemical processing takes place. Alternatively,the apparatus may further comprise a wafer carrier arrangement ontowhich the wafer can be loaded, the wafer carrier arrangement comprisinga seal which seals against a surface of the wafer, preferably an uppersurface of the wafer, wherein the transfer mechanism transfers theloaded wafer carrier arrangement between the loading port and theprocessing modules. The seal of the electrochemical wafer processingmodule may seal against a surface of the wafer carrier arrangement todefine the sealed cavity in which electrochemical processing takesplace.

The method may further comprise the step of loading the wafer onto thewafer carrier arrangement. The step of loading the wafer onto the wafercarrier arrangement may be performed prior to or as part of the step ofusing the transfer mechanism to transfer the wafer to a first waferprocessing module in the stack.

An electrical bias may be applied to the wafer during at least oneprocessing step performed on the front face of the wafer.

Two or more semiconductor wafers may be processed in parallel.

According to a third aspect of the invention there is a method ofservicing an apparatus according to the first aspect of the inventioncomprising the step of removing a wafer processing module from the stackin a substantially horizontal direction to provide access to the waferprocessing module.

Servicing may comprise performing maintenance and/or repair work on theapparatus.

The step of removing the wafer processing module from the stack in asubstantially horizontal direction may comprise rotating or sliding theprocessing module.

Whilst the invention has been described above, it extends to anyinventive combination of the features set out above or in the followingdescription, drawings or claims. For example, any feature described inrelation with the first aspect of the invention is considered to bedisclosed also in relation to any other aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of methods and apparatus in accordance with the presentinvention will now be described, by way of example only, and withreference to the accompanying drawings, in which:

FIG. 1 is a schematic view of a wafer processing system includingstacked processing modules.

FIG. 2 is a schematic view of a wafer processing system with aprocessing module removed to allow access for maintenance purposes.

FIG. 3 is a schematic view of a processing module.

FIG. 4 is an exploded schematic view of a processing module.

FIG. 5 is a perspective view of a processing module.

FIG. 6 is a plan view of a wafer processing system comprising rows ofstacked processing modules.

FIG. 7 is a side view of a wafer carrier arrangement.

Where the same reference numerals have been used in different exemplaryembodiments, the reference numerals correspond to features that areidentical.

DETAILED DESCRIPTION

FIG. 1 shows a wafer processing system 10 according to a firstembodiment of the present invention. The wafer processing system 10comprises a frame 12, a loading/unloading port 14, a robot 16 and aplurality of stacked processing modules 18 a-18 d. Other embodiments ofthe present invention may incorporate fewer or more than four processingmodules depending on the number of processing steps required and thevertical transfer reach of the transfer robot 16. The processing modulesmay each individually be suitable for wet chemical processing steps,such as electrochemical deposition, electrodeposition, electropolishing,chemical etching and the like; and cleaning, rinsing and dryingprocessing steps. All positions in the stack can accommodate any moduleconfiguration and be suitable for performing any processing step. Thehardware may be easily changed when process demands change.

The wafer processing system 10 may also comprise local fluid supplies 20located underneath the processing modules 18 a-d. The local fluidsupplies 20 may supply processing fluid, such as electrolyte, to eachprocessing module 18 a-d. Electronic control, monitoring circuitry andpower supplies for the modules (not shown) may be situated above theprocessing modules 18 a-d. Ancillary features (not shown), such as powerdistribution for the wafer processing system 10, bulk electrolytestorage and monitoring equipment may be situated remotely from the waferprocessing system 10.

The frame 12 encloses the components of the wafer processing system toprovide a contaminant-free environment in which wafer processing cantake place. A laminar airflow is produced by fan or blower 22 tomaintain a particulate-free environment within the main chamber 24.

The loading/unloading port 14 allows semiconductor wafers 28, such as300 mm diameter silicon wafers, to be loaded into and unloaded from thewafer processing system 10. The loading/unloading port 14 may be acassette or a FOUP (front opening unified pod). The port 14 may alsoserve as a wafer storage location in between processing steps.

The robot 16 comprises an end effector 26 which contacts the back faceof the wafer 28 (ie. the face of the wafer not subjected to processing)and transfers it to one of the processing modules 18 a-d. In oneembodiment, the wafer 28 is handled with the front face of the wafer(ie. the face to be processed) facing upwards during all handling andprocessing steps. In one embodiment of the invention there may alsoinclude a wafer alignment step (not shown) prior to the wafer beingtransferred to one of the processing modules 18 a-d. The use of a wafertransfer robot 16 allows automated wafer transfer between the port 14and the processing modules 18 a-d.

The processing modules 18 a-d are arranged in a vertical stack 19.Vertically stacking the processing modules 18 a-d significantly reducesthe tool footprint of the wafer processing system 10 compared with knownsystems using an equivalent number of processing modules. It ispreferable to use a low profile processing module, that is, a processingmodule with a height of less than approximately 30 cm. More preferably alow profile module will have a height of less than 22 cm. Use of a lowprofile processing module enables more efficient vertical stacking.Known fountain cell and rack type systems require a large overheadvolume in order for the substrate to enter the processing module fromabove. Consequently, known fountain cell and rack type systems are notwell suited for efficient vertical stacking.

Access may be gained to each processing module 18 a-d by sliding orrotating a processing module out of the vertical stack 19 as shown inFIG. 2 . Each processing module may be independently removable from thestack. This may be required when system intervention is required, forexample, when changing an anode or to conduct a manual clean within themodule. The isolated processing module 118 may remain connected to thewafer processing system 10 through the extendable fixture 50 to aid thereplacement of the isolated processing module. The extendable fixturemay also be attached to the frame 12. Removal of an individualprocessing module in this way enables complete and facile access to theisolated module.

A wet chemical processing module 30 suitable for incorporation into thewafer processing system 10 is shown in FIGS. 3, 4 and 5 . Waferprocessing modules suitable for incorporation into the wafer processingsystem 10 are also described in EP2781630 and EP2652178. The wafer istransferred from the end effector 26 of the robot arm to a movableplaten assembly 32 via entry slot 34. The movable platen assembly 32 maybe a rotatable platen assembly.

The platen assembly 32 is raised such that the front surface of thewafer mates with the anode chamber 35. A fluid seal is formed betweenthe front face of the wafer and an elastomeric seal 36. The elastomericseal may be frustro-conical shaped to afford a reliable fluid tightseal. Furthermore, a seal of this shape will not fall out of the chamberdue to gravity or surface tension with the surface of the wetted wafer.The elastomeric seal may be attached to the anode chamber 35.

A fluid tight seal is required to prevent fluid leaking from theprocessing module during the processing step. A containment tray 38 maybe positioned below the platen 32 to contain any fluid leaks that mayoccur.

If required, an electrical contact to the wafer 28 may also be formed sothat the wafer may serve as an electrode. The electrical contacts may beattached to the anode chamber 35. The electrical contacts may be madeusing titanium electrodes, Pt-coated titanium electrodes or electrodesmade from any other suitable electrically conducting material. Theelectrodes may contact the wafer surface in the edge exclusion area. Theedge exclusion area is typically <2-3 mm from the wafer edge. The fluidtight seal prevents the electrical contacts from becoming exposed to orcontaminated by the processing fluid.

The wafer may be a cathode or an anode depending on the processing step.For the purposes of example only, a DC bias may be applied to the waferwhen acting as a cathode in an electrochemical deposition process. Theanode in this process may be a consumable metal, such as Cu, Ni or Sn,or an inert contact, such as Pt-coated Ti or mixed metal oxide (MMO).

The wafer 28 and the anode chamber 35 define a sealed cavity 40 in whichwet chemical processing may occur. Wet chemical processing may compriseone or more of inter alia electrochemical or electroless deposition,electrochemical etching, and chemical etching. The fluid seal betweenthe wafer 28 and the anode chamber 35 is made before any fluid entersthe cavity 40. Fluid may enter and leave the cavity 40 though fluidconnectors 42 and 44. The fluid may be an electrolyte or other suitablefluid dependent upon the processing step to be performed. In oneembodiment the connector 42 is a fluid inlet whilst the connector 44 isa fluid outlet. In another embodiment the connector 42 is a fluid outletwhilst the connector 44 is a fluid inlet. It is preferable toincorporate more than one fluid connector if high fluid flow ratesthrough the processing module are required. Multiple fluid inlets helpto precisely control fluid flow rate and help to ensure gas/air pocketsdo not form in the cavity 40, which can affect the quality of theprocessing step. For example, an air pocket in an electrodeposition stepmay affect the uniformity of the resultant deposit.

The fluid is removed from the processing module 30 after the processingstep is complete and before the fluid seal between the wafer 28 and theanode chamber 35 is broken. Fluid may be removed via fluid connectors 42and 44. The processing module 30 may be tilted to aid fluid removalusing tilting bracket 46. The tilting bracket 46 is mounted on a supportplate 48. The support plate 48 may be fixed to the anode chamber 35 viaa series of retaining bolts (not shown). The fluid may be recycled foruse in future processing steps. If required, a rinse step may beperformed prior to the removal of the wafer 28 from the processingmodule 30.

A processing module may be used for cleaning, rinsing, wetting or dryingprocesses. For rinsing, cleaning or drying, the wafer 28 may be rotatedby using a rotatable platen assembly. Cleaning fluid may be jettedtowards the front face of the wafer surface for cleaning and/or wettingpurposes. After removing the cleaning fluid from the cavity 40, asubsequent high speed drying step may be initiated. The drying processmay be accelerated by rotating the platen assembly, for example up to3000 revolutions per minute (rpm). A spin rinse dry (SRD) module may beprovided which has a rotatable platen and one or more sprays.

To remove the wafer 28 from the processing module 30, the platenassembly 32 is lowered, which breaks the fluid seal. The end effector 26of the robot arm may collect the wafer 28. The wafer 28 may betransferred to a further processing module or to the loading port 14 fortemporary storage or removal from the wafer processing system 10.

The support plate 48 may be attached to an extendable fixture 50. Theextendable fixture 50 may remain connected to the processing module 30when the processing module is removed from the frame 12. The extendablefixture may comprise a means of supplying the processing module 30 withelectrical power necessary to perform electrochemical processing steps.

After the processing module 30 has been isolated from the frame 12,maintenance may be carried out on the processing module. The retainingbolts and fittings (not shown) may be removed to enable the anodechamber 35 to be detached from the module 30. The anode chamber 35 canthen either be replaced by a new chamber, refurbished or replaced asappropriate.

Access to the platen assembly 32 is provided after the anode chamber 35has been removed. Access to the platen assembly 32 may also be achievedby removal of the containment tray 38.

The processing modules 18 a-d of the wafer processing system 10 arearranged in a vertical stack 19. This is not a practical arrangement forknown wafer processing systems, such as “fountain cell” and “rack” typesystems. For these known systems, it is necessary for the electrolytebath to have an open top with a large depth to allow the wafer to befully submerged. A vertically stacked arrangement of open toppedprocessing baths would be vulnerable to contamination from theprocessing fluid in the bath above. Furthermore, a large verticalseparation (or pitch) is necessary to stack such known processing baths.Without a large vertical separation, the upper baths would at leastpartially block the entry of the wafer into the electrolyte bath fromabove. In addition the user's access to the processing baths formaintenance and cleaning purposes would also be at least partiallyrestricted. Maintenance may comprise replacing the anode in anelectrodeposition cell.

The design of the processing module 30 allows processing modules to bestacked vertically in a significantly more efficient and compactarrangement without restricting the entry of the wafer into eachprocessing module. Each processing module may also be readily accessedby removing the processing module from the vertical stack 19. This alsoallows hardware to be changed easily when process demands change.

All fluid wetted surfaces are typically fabricated using plasticmaterials such as PVC (polyvinyl chloride), HDPE (high densitypolyethylene), PVDF (polyvinylidene fluoride), PTFE(polytetrafluoroethylene), or PFA (perfluoroalkoxy). The preferredmaterial is determined by chemical compatibility, mechanical propertiesand cost.

As a consequence of the simplified handling system and processing modulearrangement, the wafer processing system 10 may be built in a costeffective fashion.

FIG. 6 shows a plan view of a second embodiment of a wafer processingsystem 210 in which vertical stacks 52 a-c of the processing modules 18a-d may be arranged in rows. Processing modules 30 of the type describedabove in relation to FIGS. 3 to 5 may be suitable for use in the waferprocessing system 210. Each processing module may be utilised for adifferent processing step as part of a larger processing procedure.

The wafer processing system 210 may have one or more loading/unloadingports 214 a-c. The ports 214 a-c allow semiconductor wafers, such as 300mm diameter silicon wafers, to be loaded into and unloaded from thewafer processing system. The loading/unloading ports 214 a-c mayindividually be cassettes or FOUPs. The ports 214 a-c may serve as waferstorage locations in between processing steps.

The transport robot 216 comprises one or more end effectors 226 each ofwhich may independently contact the back face of a wafer (ie. the faceof the wafer not subjected to processing) and transfer the wafer to oneof the processing modules 18 a-d. The transport robot 216 may travelalong a track 254 to enable access to each processing module 18 a-d ineach vertical stack 52 a-c.

The robot 216 and vertical stacks 52 a-c are housed in a frame 12. Theframe 12 provides a contaminant-free environment in which waferprocessing can take place. A laminar airflow is produced by a fan orblower to maintain a particulate-free environment within the mainchamber 224.

A wafer alignment tool 256 may also be incorporated in the main chamber224 to ensure correct wafer alignment during wafer transfer.

FIG. 6 shows a wafer processing system 210 incorporating three adjacentvertical stacks 52 a-c, however, it would be envisaged that more orfewer vertical stacks may be used. Furthermore, other spatialarrangements, rather than a simply linear system, may be envisaged toachieve an efficient tool footprint.

In the embodiments described above in relation to FIGS. 1 to 6 , thewafer itself is introduced into the processing modules. It is possibleto instead introduce the wafer into the processing modules mounted on awafer carrier arrangement. FIG. 7 shows such an embodiment, in which asemiconductor wafer 70 is positioned on a wafer carrier fixture 72. Inthe embodiment shown in FIG. 7 , the wafer carrier fixture 72 comprisesa frame 74, a seal 76, and a substrate support 78 which is incommunication with the frame 74. The frame 74 comprises an upper surface74 a and carries the seal 76. The wafer 70 is positioned on thesubstrate support 78. The wafer carrier fixture 72 further comprises anelectrical contact 80 and a feedthrough 82 for the electrical contact80. When the wafer 70 is properly positioned, the electrical contact 80makes electrical contact with the wafer 70 and the seal 76 seals againstthe wafer 70 to make a fluid tight seal. The components of the wafercarrier fixture 72 can be formed from any suitable materials. Forexample, the frame 74 is typically formed from a dielectric material andthe seal 76 is typically an elastomeric material such as Viton®.

When the wafer carrier fixture 72 with wafer 70 is loaded into aprocessing module such as an electrochemical wafer processing module, afluid seal is made between the module and the upper surface 74 a of theframe 74. The alignment constraints for this seal are less stringentthan with a fluid seal to the wafer surface. The skilled reader willreadily appreciate that there are numerous ways of making a reliableseal to the upper surface 74 a.

The wafer carrier fixture 72/wafer 70 assembly can be readilyincorporated into the apparatus described in relation to FIGS. 1 to 6without any major change in the general lay out of the system. Forexample, the wafer 70 could be inserted into the fixture 72 afterleaving the loading/unloading port 14. The wafer 70 would remain in thewafer carrier fixture 72 until after the final processing step iscarried out. An additional station or other mechanism can be providedafter the loading/unloading port 14 for loading and unloading the waferonto and from the wafer carrier fixture. Many other arrangements forcarrying the wafer and loading the wafer onto the carrier are possible.The benefit of this approach is that the seal and contacts are made onlyonce on the wafer surface.

What is claimed is:
 1. A method of processing a semiconductor waferusing an apparatus, the apparatus comprising: a main chamber; at leastone loading port connected to the main chamber for introducing the waferto the main chamber; at least one stack of wafer processing modulescomprising three or more substantially vertically stacked waferprocessing modules, wherein adjacent wafer processing modules in thestack have a vertical pitch of less than 50 cm, and each processingmodule is configured to process the wafer when disposed substantiallyhorizontally therein with a front face of the wafer facing upwards, andat least one wafer processing module is an electrochemical waferprocessing module; a transfer mechanism for transferring the waferbetween the loading port and the processing modules; and an anodechamber disposed in an opening of a support plate that extends throughthe support plate from a first surface to an opposite second surfacefacing a platen assembly, wherein the anode chamber and the supportplate are independently movable; wherein the method comprises the stepsof: introducing the wafer to the main chamber via the loading port;using the transfer mechanism to transfer the wafer to a first waferprocessing module in the stack so that the wafer is disposedsubstantially horizontally in the first wafer processing module with thefront face facing upwards; and performing a processing step on the frontface of the wafer in the first wafer processing module.
 2. The method ofclaim 1, further comprising the steps of: using the transfer mechanismto transfer the wafer from the first wafer processing module to a secondwafer processing module in the stack so that the wafer is disposedsubstantially horizontally in the second wafer processing module; andperforming a processing step on the front face of the wafer in thesecond wafer processing module.
 3. The method of claim 1, furthercomprising the step of: using the transfer mechanism to transfer thewafer from a wafer processing module to the loading port for subsequenttransfer out of the apparatus.
 4. The method of claim 1, wherein atleast one processing step performed on the front face of the wafer isselected from the group comprising a chemical, electrochemical, rinsing,cleaning, spinning, or drying step.
 5. The method of claim 4, wherein aprocessing step performed on the front face of the wafer is anelectrochemical processing step performed in the electrochemical waferprocessing module, wherein the electrochemical wafer processing modulecomprises a seal which seals against a surface to define a sealed cavityin which electrochemical processing takes place.
 6. The method of claim5, wherein the surface is an upper surface of the wafer.
 7. The methodof claim 1, wherein the apparatus further comprises: at least one wafercarrier arrangement onto which the wafer can be loaded, the wafercarrier arrangement comprising a seal which, in use, seals against asurface of the wafer wherein the transfer mechanism is configured totransfer a loaded wafer carrier arrangement between the loading port andthe processing modules.
 8. The method of claim 7, wherein the apparatusfurther comprises: a wafer carrier arrangement loading station forloading the wafer onto the wafer carrier arrangement.
 9. The method ofclaim 1, wherein the vertical pitch is less than 25 cm.
 10. The methodof claim 1, wherein the transfer mechanism comprises a transfer robothaving at least one end effector for automated transfer of the waferbetween the loading port and the processing modules.
 11. The method ofclaim 1, wherein at least one of the wafer processing modules comprisesan electrochemical deposition wafer processing module.
 12. The method ofclaim 1, wherein the front face of the wafer comprises an electrode. 13.The method of claim 1, wherein the processing modules are removable fromthe stack.
 14. The method of claim 13, wherein the processing modulesare removable from the stack in a substantially horizontal direction.15. The method of claim 13, wherein the processing modules are removablefrom the stack by rotating or sliding.
 16. The method of claim 1,wherein the apparatus further comprises: a tilting bracket for theprocessing module that is disposed on the support plate, wherein theprocessing module is configured to be tilted using the tilting bracket.17. A method of servicing an apparatus, the apparatus comprising: a mainchamber; at least one loading port connected to the main chamber forintroducing the wafer to the main chamber; at least one stack of waferprocessing modules comprising three or more substantially verticallystacked wafer processing modules, wherein adjacent wafer processingmodules in the stack have a vertical pitch of less than 50 cm, and eachprocessing module is configured to process the wafer when disposedsubstantially horizontally therein with a front face of the wafer facingupwards, and at least one wafer processing module is an electrochemicalwafer processing module; a transfer mechanism for transferring the waferbetween the loading port and the processing modules; and an anodechamber disposed in an opening of a support plate that extends throughthe support plate from a first surface to an opposite second surfacefacing a platen assembly, wherein the anode chamber and the supportplate are independently movable; wherein the method comprises the stepof: removing a wafer processing module from the stack in a substantiallyhorizontal direction for providing access to the wafer processingmodule.
 18. The method of claim 17, wherein the step of removing thewafer processing module from the stack in a substantially horizontaldirection comprises rotating or sliding the processing module.
 19. Themethod of claim 17, wherein each processing module is configured toprocess the wafer when disposed substantially horizontally therein on aplaten assembly; wherein the apparatus further comprises: a tiltingbracket for the processing module that is disposed on the support plate,wherein the processing module is configured to be tilted using thetilting bracket.